Acid-Heat Induced DNA Injury in Spores of Bacillus subtilis and Its Repair During Germination

Abstract

The effects of heating in acidic media on the survival and deoxyribonucleic acid (DNA) lesion of spores were studied in comparison with those in neutral pH media. The repair of heat-injured DNA in germinating spores was also studied. By heating at 70°C for 60min in neutral pH medium, DNA in spores was scarcely injured, but at pH 5.0 much of the spore DNA was broken. It is thought that the acid-heating introduces alkali-labile lesions(apurinic sites) in DNA. There fore, the DNA breakage in this case probably took place through 2 steps, namely (1) the depurination by acid-heating and (2) the subsequent split of the depurinated sites by alkaline treatment.
When the spores of B. subtilis which were heated at 70°C for 20 min at pH 5.0, were incubated in germination medium at 37°C for 120 min, the alkaline labile sites in DNA were restored. Under this condition the number of survivals was not much reduced. The process of DNA repair corresponded to the DNA synthesis during germination.